you may consider to look at the following links for custom date picker
using NSCalendar class
https://github.com/mwermuth/MWDatePicker
http://blog.deeplink.me/post/81386967477/how-to-easily-customize-uidatepicker-for-ios

I figured it out, this may not color the nav bar, but it gives me the
desired result:
tintManager.setNavigationBarTintEnabled(false);
This line set the nav bar to clear, which was my desired result.
I also found:
tintManager.setNavigationBarTintColor(Color.BLACK);
which can set the nav bar to any color.
I am closing this question with this answer.

You might need to create an array to keep the cells that are selected
thus background color is changed.
Also you will need to change the ng-click function to check the array,
and implement the following logic "if there is a record for the
clicked row as selected change it's bg-color to yellow"

To generate a gradient between two color values, you can just linearly
interpolate between them. This will basically work in any color
space, although if the transformation between two color spaces is not
linear, the gradient obtained by linearly interpolating in one space
will not be linear in the other. Thus, generating gradients in Lab
color space is exactly like generating them in, say, RGB